The present invention relates to a device and also to a method for detecting displacement of an object. The displacement detected may be manifested in a number of forms, including movement, elongation (e.g., caused by a stress or change in temperature), deformation (e.g., of a diaphragm), and vibration. The invention is particularly useful in medical applications, e.g., for detecting respiration or pulse-rate but may also be used in a wide variety of non-medical applications, some of which are described below for purposes of example.
With respect to medical applications, several problems are present when monitoring vital signs of anesthetized patients, particularly infants and children unable to keep still during MRI (magnetic resonance imaging) procedures. Thus, when metallic electrodes and wires are used for this purpose, the metal in the electrodes and wires interfere with the image quality. In addition, the strong pulsating fields produced during the MRI procedure generate undesirable noise signals which interfere with the ECG and respiration monitors.